1. Field of the Invention
The present invention relates generally to systems for repairing conduit, such as utilizing a conduit expansion process and, in particular, to a bladder system with accompanying hardware for expanding a liner conduit within a host conduit in such a conduit expansion process.
2. Description of Related Art
Conduit systems are used extensively throughout the world in order to transfer or convey material, such as water and other fluids, from location to location for distribution throughout the system. For example, extensive conduit systems are used to distribute water to both residences and businesses for use and further processes. Typically, such conduit or piping systems are located underground, as aboveground piping would be both unsightly and intrusive.
Typical water conduit systems transport material through pipe, e.g., cast iron, ductile iron, reinforced concrete, cement-asbestos, etc., buried underground with the branches extending in various directions in order to reach the end user. Normally, after many years of use, or for some other reason, the present piping fails and begins to leak, thereby reducing line pressure and unnecessarily allowing water to leak into the area surrounding the piping. Such leaks not only affect the system, but increase the processing costs of the supplier, which, in turn, increases the end user costs. Therefore, these leaks must be quickly repaired and preventative measures taken to ensure that further leakage is prevented.
Due to the underground positioning of the conduit system, repairing a leaking pipe is particularly labor intensive and time consuming. Trenches must be dug along the pipeline to locate the leak and effectively repair it prior to putting the pipe back in service. Various lining systems have been developed according to the prior art in an attempt to seal a leaking pipe or a pipe that has fallen into disrepair, whether to repair a present crack or to preventatively ensure against future cracks or breaks. In addition, the use of a much smaller diameter pipe within the larger diameter cracked or broken pipe has been used. However, this merely replaces the problem of a cracked outer pipe with a cracked or otherwise leaking inner pipe. Still further, using such a pipe-in-pipe system drastically reduces the flow through the conduit system and evidences unwanted and varying pressure parameters.
To that end, a pipe liner and method of installation have been developed, as disclosed in U.S. Pat. No. 5,794,662 to St. Onge et al., specifically directed to pressurized pipeline applications. The St. Onge patent is directed to a method of relining sewer lines, water lines or gas lines, and uses a segmented liner of reduced size relative to the pipe being relined. However, as opposed to merely leaving the small diameter liner conduit within the large diameter outer conduit, the method of the St. Onge patent uses heat and/or pressure to mold the reduced size pipe to the shape of the pipe being relined. In particular, the inner or liner conduit is a thermoplastic pipe, typically a polyvinyl chloride (PVC) pipe that, when exposed to heat or pressure, expands and molds against the inside of an existing conduit to effect the relining of it. This process allows for both the lining of the entire length of pipe or only a portion of it that is damaged, which is typically referred to as “spot repair.”
According to the St. Onge patent, once the length of the liner conduit is inserted into the existing or host conduit, the liner conduit is plugged at either end and exposed to steam under pressure to heat the liner conduit along its length and apply pressure, which urges it to expand and contact the interior walls of the surrounding host conduit. Once the liner conduit has fully expanded to conform to the interior surface of the existing conduit, it is cooled and the plugs are removed. The resulting expanded liner conduit conforms to the walls of the host conduit, thereby preventing any further leakage. Also, the method of the St. Onge patent requires only pits to be dug at either end of the section to be repaired.
While the St. Onge patent represents an advance in the art of relining and repairing underground conduit systems, there is room in the art for additional improvements and advancements. Various systems and processes have been developed for repairing damaged conduit. For example, see U.S. Pat. No.: 5,855,729 to Kiest, Jr. et al; U.S. Pat. No. 5,487,411 to Goncalves; U.S. Pat. No. 5,346,658 to Gargiulo; U.S. Pat. No. 6,093,363 to Polivka; U.S. Pat. No. 5,397,513 to Steketee, Jr.; U.S. Pat. No. 5,346,658 to Gargiulo; U.S. Pat. No. 5,706,861 to Wood et al.; U.S. Pat. No. 5,368,809 to Steketee, Jr.; U.S. Pat. No. 4,671,840 to Renaud; U.S. Pat. No. 5,927,341 to Taylor; U.S. Pat. No. 5,503,190 and U.S. Pat. No. 5,490,964 to Kamiyama et al.; U.S. Pat. No. 4,361,451 to Renaud; and U.S. Pat. No. 6,539,979 to Driver; and Publication No. 2003/0015247 to Driver et al. However, such systems and processes have several drawbacks based upon their advanced structural and mechanical setup, as well as the complex methods of installation and operation. In order to expand the liner conduit within the host conduit, mechanical systems and fittings are required at both ends of the liner conduit, as inserted in the host conduit. In addition, this hardware must be attached directly to both the liner conduit and the host conduit, which requires further and more labor-intensive interaction between the installers and the buried conduit system. Therefore, when using hardware that must be attached directly to the liner conduit and/or the host conduit, a significantly larger trench is required, such that at least one person can be positioned immediately adjacent the ends of the liner conduit and/or the host conduit for making the appropriate connections and engaging the fittings of the hardware of the system.